Electrodeposition, among other processes, is used as a manufacturing technique for the application of films (e.g.; metal films) to various structures and surfaces, such as semiconductor wafers and silicon workpieces. An important feature of systems used for such processes is their ability to produce films with uniform and repeatable characteristics such as film thickness, composition, and profile relative to the underlying workpiece profile.
Such films can be produced on three dimensional structures in the 1 to 100 micron scale, e.g., voids, vias, cavities, or features on a workpiece surface. A difficulty encountered when electroplating on such structures in a workpiece, whether holes in the workpiece itself, or holes in a photoresist masking film on the workpiece, is wetting the structure. Water and other fluids such as acidic or basic chemistry baths can be used in electrodeposition or electroless deposition. For micron-sized features, the relative strengths of the surface tension forces and viscous forces compared to the fluid mass acceleration or gravitational forces can be different than for large-scale features of 1 millimeter or more. Cohesive forces in the fluid tend to prohibit the fluid from flowing into small features, and therefore it can be difficult to wet such small features with existing methods, such as spraying the fluid through a high-pressure nozzle.
Vacuum impregnation has been used in various other processing applications, such as injection molding. Vacuum impregnation has not been applied to silicon wafer manufacturing or electrodeposition due to the difficulty of achieving a vacuum simultaneously on the front and back surfaces of the workpiece while maintaining a fluid seal to prohibit the fluid from reaching the edge or backside of the workpiece. Without minimizing the pressure differential between the front and back surfaces, the workpiece can be damaged, bowed, or fractured. Such a method and apparatus also has not previously been considered as a method for wetting wafers for electroless deposition.
Prior art systems suffer from one or more of these limitations, and a need therefore exists for new and improved methods and apparatuses for controlling pressure on both sides of one or more wafers in a manner that allows automatic and/or high-speed wetting of the workpiece surface prior to electrodeposition, electroless deposition, or other wafer-level processes.